An uninterruptible power supply, well known as a UPS, is typically used as a buffer between commercially supplied power and an electrical load, such as a computer, blood analyzer or other electronic equipment. If line voltage is interrupted, power to the load is maintained for a limited amount of time to operate the load during the interruption or to provide time to properly shut down the load without resulting damage. An on-line UPS typically comprises a converter, inverter, and battery charger. The UPS converts the commercially supplied AC power to DC power and then back to AC power. This conversion isolates the load equipment from spikes and sags in the commercially supplied power and corrects variances in line voltages. DC power is used to charge a battery. The battery can then be used to supply AC power to the load when the commercially supplied power is interrupted.
In commercial applications, loads may change over time. As computer networks are expanded the load on the UPS increases. In order to meet this increase in demand, either a larger UPS is needed or a plurality of modular UPS units can be connected together to meet the required power level.
Some illustrative UPS systems include those manufactured by the present assignee, Toshiba International Corporation, including, e.g., models which offer in tower design solutions. Some illustrative UPS designs are able to supply uninterrupted, clean single-phase power to systems while keeping batteries charged continuously, even if the utility power fails. Under normal operating conditions, the UPS's rectifier converts alternating current (AC power) to direct current (DC power), which is required for the system's inverter and battery charger. The charger supplies regulated DC power to keep the batteries constantly charged. The inverter uses pulse width modulation (PWM) that fully utilizes the characteristics of insulated-gate bipolar transistors (IGBT) to convert DC power to regulated AC power. Therefore there is a constant supply of power. The batteries will instantaneously supply the inverter DC power should an AC power line failure occur. AC input from the utility system is converted into DC power chopper. The stepped up DC power is then convened to AC power by the inverter. The output voltage waveform of the inverter will be the pulse voltage waveform modulated by the PWM control. The PWM-Modulated voltage waveform is transformed into a sine voltage waveform by the inductive component of the inverter inductor and by the capacitive component of the capacitor filter. The chopper, inverter and charger use the IGBT with a self-extinguishing function and a high switching speed. On the output there is an isolation transformer for extra power conditioning. In some examples, the UPS system employs the following Modes of Operation:
Emergency (Battery Backup)—In the event the AC power from the utility system fails, the DC power is supplied from the batteries to the chopper and to the inverter to provide a continued and stable AC power supply to the load without interruption.
Normal (Inverter)—The rectifier converts AC to DC to power the inverter, which supplies power to the critical load and simultaneously float charging the batteries.
Battery Charge—The charger will float charge the batteries while no load is being powered by normal mode.
Static Bypass—If the UPS unit is in severely overloaded or develops an internal faults, power is automatically switched from the units main circuit to the bypass circuit. Power is conditioned by line filters, and the isolation transformer during static bypass operation.
An illustrative UPS system includes status and control indicators, and includes a panel on the front for monitoring control of the UPS. In this regard, operation panel features include: 1) Run/Stop button; 2) AC input voltage indicator, 3) Inverter status indicator; 4) Alarm indicator; 5) Fault indicator; and a 6) Liquid Crystal Display (LCOD). The UPS has a LCD that displays operating conditions, warning messages and fault indication messages for the unit. In this regard, Operating Conditions Display can include e.g.: 1) Input voltage; 2) Output voltage, 3) Input frequency, 4) Output frequency; 5) Output current; 6) Battery voltage; 7) Battery test results; 8) Output voltage adjustment; 9) UPS ON/OFF Line. Moreover, Warning Messages can include, e.g.: 1) Overload; 2) Current limit 3) Emergency power off; 4) Battery discharge; 5) Battery Low-6) Input undervoltage; 7) Battery not good. Moreover, Fault Messages can include, e.g.: 1) DC undervoltage; 2) DC overcurrent; 3) DC overvoltage; 4) Overheat, 5) UPS overload; 6) Inverter undervoltage; and 7) Inverter overvoltage.
Although a variety of UPS systems are known in the art, there remains a need for improvements in relation to user management and use of such systems, including user operation of such systems via existing user interfaces. Some illustrative background UPS systems are shown in the following U.S. patents and applications of the present assignee (Toshiba International Corporation), the entire disclosures of which are incorporated herein by reference: U.S. Pat. No. 6,317,348; U.S. patent application Ser. No. 11/676,460; and U.S. patent application Ser. No. 11/737,427. By way of example, an illustrative background UPS device of the present assignee, Toshiba International Corporation is shown in FIG. 1.